Synthesis, crystal structure and Hirshfeld surface analysis of [1-(4-bromophenyl)-1H-1,2,3-triazol-4-yl]methyl 2-(4-nitrophenoxy)acetate

The title molecule has a twisted conformation and is connected with its neighbours by C—H⋯O and C—H⋯N hydrogen bonds, π–π and Br–π interactions.


Chemical context
1,3-Dipolar cycloaddition, a reaction between a 1,3-dipole and a dipolarophile to generate a five-membered ring, has been known since the early 20th century, following the discovery of 1,3-dipoles; its mechanism was studied and synthetic applications were developed in the 1960s, primarily through the work of Rolf Huisgen (Bertrand et al., 1994;Huisgen, 1963).Meldal and Sharpless independently developed a copper(I)-catalysed version of the Huisgen cycloaddition reaction (Tornøe et al., 2002;Rostovtsev et al., 2002), which earned the name of 'click chemistry' for its versatility.They found that only one isomer, 1,4-disubstituted 1,2,3-triazole, was formed from the cycloaddition of terminal alkyne and organic azides under these conditions.The mechanism of the reaction and the role of the Cu I salt were fully explained.Currently, 1,2,3-triazole derivatives are researched intensively because of their pharmacological and biological activity (Borgati et al., 2013;Bozorov et al., 2019;Faraz et al., 2017;Li et al., 2015).In the course these studies, we prepared the title compound 1 by the cross-ring reaction of 4-nitrophenoxyacetic acid propargyl ether with para-bromophenylazide and characterized it by single-crystal X-ray diffraction and NMR spectroscopy.

Figure 2
Crystal packing of 1, showing hydrogen bonds, �-�-and Br-� interactions as blue, green and red dotted lines, respectively.The centroids of the triazole (Cg1) and brominated phenyl (Cg2) rings are shown by blue and red circles, respectively.H atoms not participating in hydrogen bonds are omitted.

Figure 3
Hirshfeld surface of 1 mapped over d norm and close intermolecular contacts.

Figure 4
Two-dimensional fingerprint plots of the intermolecular contacts in 1.

Synthesis of 1.
1.00 g (5 mmol) of para-bromophenylazide, 1.175 g (5 mmol) of prop-2-yn-1-yl-2-(4-nitrophenoxy) acetate, 0.10 g (0.32 mmol) of CuBr and 30 ml of toluene were placed into a flask with a reflux condenser, which was heated on an oil bath at the boiling point of toluene (383 K) for 6 h.The progress of the reaction was monitored by thin-layer chromatography.Over time, a precipitate began to form in the reaction mixture.After 6 h, the reaction was stopped and it was left overnight at room temperature.The precipitate was filtered, dried and recrystallized from ethanol, yielding 1.717 g (79.3%) of 1, m.p. 417-419 K, R f = 0.55 (system benzene:methanol, 10:1).Colourless single crystals suitable for X-ray diffraction analysis were grown from ethanol at room temperature over two weeks.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms attached to C were positioned geometrically, with C-H = 0.93 A ˚for aromatic or C-H = 0.97 A ˚for methylene C atoms, and were refined as riding with U iso (H) = 1.2U eq (C).

Special details
Geometry.All esds (except the esd in the dihedral angle between two l.s.planes) are estimated using the full covariance matrix.The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry.An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s.planes.

Table 2
Experimental details.